Jogging strollers (also referred to as running strollers, walking carriages, jogging carriages and running carriages) are a popular means by which adult attendants can take their babies, toddlers and small children along when the adult attendants are engaged in walking, jogging, or running exercises. The vast majority of commercially available jogging strollers are pushed by the attendant. Push-type strollers require that the attendant use one or both of his or her arms and hands to propel and control the stroller during operation. This requirement restricts arm swing that naturally occurs in humans during walking and running. Arm swing during running, at any speed, affects factors such as center of mass; forward propulsion; and various components of angular momentum. Therefore, restricted arm swing can affect critical factors that mediate the biomechanical efficiencies inherent in human locomotion.
Steering mechanisms employed by push-type strollers may compromise the safety of the child and the attendant at higher travel velocities. Steering designs often employed by push-type strollers include front wheels that swivel or caster to allow the attendant to steer the stroller while maintaining wheel contact with the ground at all times. Similar to shopping cart wheels, the front caster(s) used for push-type strollers tend(s) to “shimmy” as the stroller is propelled at higher velocities and could create lateral instability localized at the front end of the stroller. This instability could result in loss of steering control at increased travel speeds and thus compromise the child's safety. When subjected to uneven travel surfaces or obstacles along the path, such as a pebble, the direction of the affected caster tends to deviate from the path of progression, potentially resulting in abrupt changes in stroller direction that may further compromise control of the stroller. Strollers designed for higher jogging speeds often employ three wheels with a non-caster front wheel. To steer this type of stroller, the front wheel must be lifted away from the ground. This maneuver requires that the runner press downwardly on the rear stroller handle, using the rear wheel axle as a fulcrum by which to lift the front wheel up and away from the ground sufficiently to turn the stroller laterally, either completely or incrementally, in the desired direction. The weight of the stroller and the occupant is borne over the rear axle and is solely dependent on the stability and strength of the attendant's arm(s) to maintain balance during this maneuver. Some manufacturers offer front wheel designs that may be placed in either the fixed or swivel position but recommend that users lock the wheel in the “forward” position when operating the stroller at higher jogging speeds for the safety reasons stated above.
The vertical load component of known “hands-free” stroller designs result in decreased biomechanical running efficiencies due to the additional vertical load(s) placed on the attendant, and produce a jarring interaction between attendant and carriage (and child) generated by the attendant's movements, especially at higher running velocities.
When walking, jogging, or running, a person typically exhibits some lateral motion that can be translated to the carriage (and therefore the child passenger) via the tow bar. Control of this motion is especially critical for two wheeled vehicles, given the possibility that the resulting side-to-side carriage motion, as it periodically changes direction of the carriage's inertia (from left to right and right to left), could achieve a resonant frequency that could result in loss of steering control or, at minimum, result in a jarring motion for both the attendant and the child.
Furthermore, the attendant's walking/jogging/running motion may create anterior/posterior impulses between the attendant and the carriage during operation. In bipedal human locomotion, whether walking or running, the attendant's COG accelerates upon “push off” and decelerates upon “heel contact” of each step. This anterior/posterior acceleration/deceleration is translated to the carriage assembly and occupant via the tow bar—albeit asynchronously. Upon “push off,” the attendant's COG accelerates along the path of progression and the carriage experiences a corresponding acceleration. Upon heel contact, the attendant's COG decelerates. Due to the inertia of the carriage, however, the corresponding carriage deceleration will lag behind that of the attendant's deceleration, thus establishing a cycle by which the acceleration/deceleration of the carriage and attendant will be out of phase. This repetitive action generates a jarring impulse experienced at each end of the tow bar by both the attendant and the carriage at each of the attendant's steps.